I find 1928 NC to be an ever more curious case than 1928 AL. Hoover won it by nearly 10 points, despite John Davis winning it by 20 in 1924 and then FDR winning it by 40 in 1932. The 1932 swing is somewhat explainable with the realignment, but Hoover managed to swing it almost 30 points R in 1928 despite a 7.8-point national D swing.
Similar to Alabama (with Thomas Heflin), there was considerable anti-Smith sentiment at the high political levels in North Carolina. Senator F.M. Simmons went hard against the Democrats (especially on the Prohibition issue), and other Democrats in the state openly endorsed Hoover.
Interestingly, in 1930, both Simmons and Heflin lost re-election at the primary level--mainly for antagonizing the Democratic establishment in their respective states.